ABSTRACT
Meloidogyne enterolobii is an extremely important plant parasitic nematode. Tomato (Solanum lycopersicum) is an essential worldwide vegetable, and M. enterolobii poses a major threat to its production. The present research investigated the effects of different levels of inoculum density of M. enterolobii (100, 500, 1000, 1500, and 2000 second-stage juveniles (J2s)/plant) on tomato growth, physiological, and biochemical changes at 7, 14, 21, and 28 days post-inoculation (dpi). The negative impact of M. enterolobii on plants gradually increased when the inoculum level increased. Therefore, M. enterolobii population densities (500-2000 J2s/plant) significantly (p < 0.05) reduced plant growth, photosynthetic pigmentation, gas exchange, and chlorophyll fluorescence compared to control plants, while the low population density (100 J2s/plant) showed very little influence. Furthermore, plants with the highest M. enterolobii inoculum (2000 J2s/plant) exhibited a greater number of egg masses and galls. The inoculum densities of M. enterolobii exhibited a notable correlation with the significant elevation of both malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels, which are recognized as very detrimental stresses in plants. Similarly, a rise in the activity of several defensive antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), indicates the defensive mechanism used to combat the oxidative destruction produced by M. enterolobii. The specific activity of glutathione (GSH) and ascorbate (ASA) increased as potent antioxidant defense molecules in response to induced oxidative damage. In addition, our findings also demonstrated that the highest population density (2000 J2s/plant) increased the secondary metabolites responsible for scavenging oxidative stress in the plants. However, further research is required to explore the underlying reasons for this phenomenon and to develop efficient chemical or biocontrol strategies for managing M. enterolobii.
ABSTRACT
PURPOSE: Chronic Helicobacter pylori infection causes peptic ulcers in a subpopulation of individuals and is a risk factor for the development of gastric cancer. Multiple infections and heteroresistant H. pylori contribute to poor treatment efficacy. Here, we investigated the extent of genetic diversity among H. pylori strains within a given host and its influence on the results of antibiotic (metronidazole, levofloxacin, clarithromycin, amoxicillin, and tetracycline) susceptibility testing. MATERIALS AND METHODS: Gastric mucosa biopsy samples were obtained from patients with gastric disorders, including 48 H. pylori positive patients, who were never previously treated for H. pylori infection. Five potential H. pylori colonies isolated from each sample were subcultured for enrichment. Enriched H. pylori colonies were identified through Gram staining and assays for urease, oxidase, and catalase. For each H. pylori monoclonal colony, the antibiotic susceptibility was assessed, genomic DNA was sequenced, and the cytotoxin-associated gene A (cagA) genotype was verified. Co-infection with multiple H. pylori strains was determined using random amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR). RESULTS: Thirteen gastric mucosa biopsy samples were positive for H. pylori. Five monoclonal strains isolated from each of these 13 patients were identified as H. pylori. RAPD-PCR indicated that intra-patient monoclonal strains of H. pylori in 10 of the 13 samples exhibited heterogeneity. Among the 13 patients, intra-patient monoclonal strains isolated from 4 patients had identical cagA genotype, whereas intra-patient monoclonal strains isolated from the other 9 patients harbored more than one cagA genotype. The antibiotic susceptibility of five intra-patient monoclonal strains from seven patients was inconsistent. CONCLUSION: The existence of heterogeneous H. pylori strains with resistance to different drugs and virulence were common within the gastric mucosa of an individual patient.
ABSTRACT
Despite extensive studies on the gastric microbiota, including Helicobacter pylori and non-H. pylori, the bacterial composition in children remains unknown. In this study, we analyzed the culturable gastric bacteria in stomach biopsies from 346 children aged 1-15 years affected by gastric diseases. H. pylori and non-H. pylori were identified by specific PCR and 16S rDNA sequencing, respectively. Antibiotic susceptibilities of H. pylori and non-H. pylori were tested by the E-test and disk diffusion methods, respectively. Rapid diagnosis was also performed by H. pylori-specific PCR. Twenty-two H. pylori strains were obtained from culture, and 92 biopsies were positive by H. pylori-specific PCR. The positive rate was higher in boys (40.3%) than in girls (23.3%) (P = 0.001). Resistance rates of 22 H. pylori strains were as follows: metronidazole, 86.4%; tetracycline, 22.7%; amoxicillin, 22.7%; levofloxacin, 31.8%; clarithromycin, 36.4%. Ten isolates were multidrug-resistant. Additionally, among 366 non-H. pylori strains, 204 exhibited urease activity. Non-H. pylori resistance rates were as follows: metronidazole, 94.8%; tetracycline, 26.2%; amoxicillin, 42.6%; levofloxacin, 15.3%; clarithromycin, 46.7%. Our results showed that children with gastric disorders harbor stomach bacteria with urease activity or nitrate reductase activity. Further studies will determine the effects of non-H. pylori bacteria in gastric diseases.
